Leak down device for tire pressure monitoring system

ABSTRACT

A tire and wheel rim assembly includes a tire supporting rim having an outward facing mounting surface; a tire mounted to the rim positioning an internal tire cavity over the rim mounting surface; a passageway extending through the rim for communicating air pressure between the tire cavity and a side of the rim opposite the tire cavity; and means for controllably regulating the flow of air through the passageway. A connecting member such as a bolt may extend through the rim outside mounting surface to affix a tire pressure monitoring housing to the rim and the axial passageway through the rim may be an axial bore through the bolt. Regulation of air flow through the passageway may be effected by setting the diameter of the passageway sufficiently small; or incorporating a needle orifice in the passageway; or incorporating a porous insert body into the passageway. The insert body may be composed of sintered metal and may be fused to the internal sidewalls of the bolt.

FIELD OF THE INVENTION

The invention relates generally to tire pressure monitoring systems and,more specifically, to housing assemblies for such systems.

BACKGROUND OF THE INVENTION

Typical commercially available tire pressure monitoring system units aremounted to the inside of a tire in a position from which the airpressure within the tire cavity may be measured. Data representingpressure within the tire is then communicated by a transmitted signal toa reader external to the tire. For example, certain available unitsintegrate a pressure sensing module with the valve stem of a tire.Electronics within the sensor unit measure the air pressure at the valvestem and transmit an appropriate signal to an external receiver. Thereceiver may be proximally located to the sensor unit or in a remotelocation such as the passenger compartment.

While working well, such systems are not useful in meeting theindustry's needs in certain applications. For example, in someapplications, such as in NASCAR race tires, there is a need for a tirepressure-measuring device that may be used conveniently in a two tiresystem by officials to check start inflation pressure. A rim-mountedtire pressure monitoring system has been proposed and is the subject ofco-pending U.S. patent application Ser. No. 11/641,333 filed Dec. 19,2006, incorporated herein by reference.

In a rim mounted system, a housing typically molded of plastics materialis employed to house sensor and communication electronics. The housinghas an internal pressure chamber; a pressure sensing device within thehousing pressure chamber, and a portal communicating through the wheelrim between the internal housing pressure chamber and a tire air cavity.The TPMS housing unit is mounted to a rim ledge with a bolt. The bolthas a hole drilled therethrough to allow communication of the inflationpressure within the tire to the pressure chamber within the TPMShousing. The bolt threads into a threaded insert nut that is molded intothe plastic TPMS housing. An appropriate seal is used between the insertnut and the rim. In other systems, a pipe is attached to a portal withinthe rim through which pressure is communicated with the housing pressurechamber. The pipe routes along an outer rim surface to a different rimlocation where the pipe attaches to a second portal through the rim.

While working well, a rim mounted TPMS housing is exposed to potentiallydamaging external forces. It is possible for the TPMS housing to becomedamaged and even disconnected from the rim ledge mounting surface undercertain situations. In such an event, the air within the tire will leakrapidly out of the hole in the bolt, potentially resulting in loss ofcontrol of the vehicle. In a dual portal system utilizing a pipeextending between two passageways in the rim, damage to the pipe or theTPMS housing can result in the exposure of a passageway and resultantrapid loss of air from a tire. In applications where the vehicle isdriven at high speed, such as NASCAR racing, it is even more importantto prevent rapid pressure loss in a tire that can negatively impact thedriver's control of the vehicle.

Accordingly, a need exists in rim-mounted TPMS systems for a means toavoid rapid deflation of a tire through a rim portal in the event thatthe portal becomes exposed. Exposure of a portal may occur where anexternal TPMS housing becomes damaged or detached from the rim or whereancillary hardware such as a connector pipe detaches from a portal in awheel rim. Ideally, the solution to the industry's needs would becapable of giving the driver a warning early enough to allow the driverto take corrective action before tire inflation crosses over a criticalsafety threshold.

SUMMARY OF THE INVENTION

Pursuant to one aspect of the invention a tire and wheel rim assemblyincludes a tire supporting rim having an outward facing mountingsurface; at least one tire body mounted to the rim positioning aninternal tire cavity over the rim mounting surface; a passagewayextending through the rim for communicating air pressure between thetire cavity and a side of the rim opposite the tire cavity; and meansfor controllably regulating the flow of air through the passageway.

According to another aspect of the invention, a tire pressure monitoringmodule assembly is provided including a housing having an internalpressure chamber; a pressure sensing device within the housing pressurechamber; an elongate connecting member extending through the housing andthe rim mounting surface, the passageway extending axially through theconnecting member in communication with the internal tire cavity and thehousing pressure chamber.

In a further aspect of the invention, the connecting member is a boltextending through the rim outside mounting surface and the axialpassageway extends through the bolt.

Regulation of air flow through the passageway may be by setting thediameter of the passageway sufficiently small; or incorporating a needleorifice in the passageway; or incorporating a porous insert body intothe passageway. The insert body may be composed of sintered metal andmay be fused to the internal sidewalls of the bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 is a perspective view of a tire rim portion having a tirepressure monitoring module (TPMM) mounted thereto.

FIG. 2 is an exploded perspective view of a rim portion and tirepressure monitoring module configured pursuant to the invention.

FIG. 3 is a transverse section view through a tire rim portion having apair of tire bodies mounted thereto, and a tire pressure monitoringmodule mounted to the rim portion pursuant to the invention.

FIG. 4 is a perspective view of the TPMM housing.

FIG. 5 is a top plan view of the TPMM housing.

FIG. 6 is a front elevation view of the TPMM housing.

FIG. 7 is a transverse section view through the TPMM housing taken alongthe line 7-7 of FIG. 6.

FIG. 8 is a top perspective view of the insert body.

FIG. 9 is a transverse section view through the insert body taken alongthe line 9-9 of FIG. 8.

FIG. 10 is a front perspective view of the housing cover.

FIG. 11 is a side elevation view of the housing cover.

FIG. 12 is a front elevation view of the housing cover.

FIG. 13 is an end elevation view of the housing cover.

FIG. 14 is a plan view of the gasket component of the TPMM.

FIG. 15 is a sectional view through the gasket taken along the line15-15 of FIG. 14.

FIG. 16 is a front perspective view of the gasket.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1, 2, and 3, a tire, rim, and tire pressuremonitoring module assembly 10 is shown. The rim 12 is of a conventionalrim configuration. A two tire system, such as that used in NASCARracing, is depicted for the purpose of illustration, it being understoodthat the subject rim mounted tire pressure monitoring system is capableof utilization in a single tire and rim application. A pair of spacedapart tire bodies 14, 16 of conventional tire configuration is mountedto the rim 12, the tire body 16 representing an inner tire and the tirebody 14 representing an outer tire. The inner tire 16 functions tomaintain stability in the event the outer tire 14 is damaged orotherwise deflates. In a two tire system such as that shown, both tiresare mounted to a common rim internal surface region 20. With the beadsof the tire bodies 14, 16 properly seated on surface 20, the inner tire16 (which has higher inflation pressure than the outer tire) pushes bothbeads against the rim flange 22. The inner tire 16 is formed to providemolded grooves 88 to allow the inflation pressure in the cavity 30 ofthe outer tire 14 to reach the area adjacent to the flange between thetwo beads for tire pressure measurement.

As described above, the air pressure within the tire cavity 32 of theinner tire 16 is maintained higher than the pressure of the outer tirebody 14. In order to achieve competitive equality between racing carsand for safety considerations, the air pressure within the tire body 14is monitored. A tire pressure monitoring module 18 is employed for thispurpose. Module 18 is mounted to an outward facing rim surface 24adjacent a rim well wall 26. As best seen from a collectiveconsideration of FIGS. 1, 2, and 3, the module 18 includes a casing orhousing 34, an end cap 36, an annular body 38, a gasket 40, a circuitboard 41, a sealing washer 42, and bolt 44.

With reference to FIGS. 4, 5, 6, and 7, the module housing 34 includesan internal pressure chamber 46 enclosed by three sidewalls 47 and endcap 36. An internal shoulder 48 is formed within the chamber 46 oppositean open side 58. A generally circular collar 52 projects from thehousing 34 and an annular shoulder 50 projects into a collar passageway56. The passageway 56 extends through the collar 52 and the annularshoulder 50 into communicating relationship with the chamber 46. A pairof circuit board supporting rail flanges 54 extends along the interiorof the housing 34 as shown and a flat surface 57 is formed in a side ofthe collar defining bore 56. The housing 34 may be formed from anysuitable material such as moldable thermoplastic or thermoset plasticsmaterial having sufficient temperature and strength characteristics forstrength and dimensional stability in a tire/wheel rim environment.

As shown in FIGS. 10, 11, 12, and 13, the end cap 36 is a generallyrectangular cap formed of suitable material such as the material ofhousing 34. The end cap is attached securely to the housing 34 by laserwelding, ultrasonic welding, adhesive or other suitable means to enclosethe opening 58 and includes a pair of integrally molded projectingprotrusions 60 and a pair of protrusions 62. Protrusions 60, 62 locatethe end cap 36 into the housing opening. The end cap 36 further has aspaced apart pair of T-shaped protrusions 64. The circuit board 41 isinserted through the opening 58 and positioned on the support railflanges 54. The board may then be slid into the chamber 46 of housing 34until abutment. Thereafter, the end cap 36 is securely attached byappropriate means to the housing 34 over the opening 58. Secureattachment of end cap 36 to the housing 34 creates an airtight sealbetween the end cap and the housing such that air within the chamber 46cannot escape. Protrusions 64 engage the circuit board 41 within thechamber 46 to fix the board 41 in place and deter movement of the boardwithin the housing 34.

As will be appreciated from FIGS. 8 and 9, the annular body 38 isdimensioned and configured to seat within the housing opening 56 andincludes a flat surface 66 that registers opposite the flat surface 57of the housing collar 52. So positioned, the insert body 38 isconstrained from rotating within the housing collar 52. The annularshoulder 50 of the collar 52 is positioned within an annular groove 68in the annular body 38 and acts to locate and secure the insert bodywithin the collar 52. The annular body 38 is formed having a threadedthrough bore 70. The body 38 may be formed of any suitable materialhaving requisite strength. The annular body 38 is preferably althoughnot necessarily formed of stainless steel having internal threads toaccept the mounting bolt 44. The bolt 44 is likewise preferably formedof metal. Washer 42 is preferably formed of a composite material. Themetal-to-metal contact between the annular body 38, the washer 42, thebolt 44 and the rim 12 eliminates compression stress on the plastichousing 34.

The mounting bolt 44 is externally threaded and includes a bolt head 72and an axial through bore 74. The bolt may be approximately ¼ inches inlength with a 0.080 inch diameter through bore 74. It will beappreciated that the module 18 is exposed to external contact andforces. Such forces may be sufficient to break off the module 18 fromthe rim surface 24, leaving the attachment bolt 44 inside the rim. Theair from the tire cavity 30 in such an event would thereupon freelyescape from the cavity through the bolt passageway 74 at a rapid rate.The resulting rapid loss of air pressure in the tire 14 coulddestabilize the car and result in a loss of control.

In order to control the tire inflation leak down rate in the event thatthe module detaches, leaving the bolt 44 in the rim, the bolt 44 mayincorporate air flow rate regulation within the bore 74 to slow the rateof air loss from the tire 14. The air flow rate through the bore 74 maybe reduced by making the diameter of the bore 74 sufficiently small soas to only allow evacuation of air therethrough at a low rate.

An alternative means for constricting air flow through the passageway 74would be to incorporate a small orifice hypodermic needle (not shown) ofa type commercially available into the bolt passageway 74 to effectivelyreduce the diameter of the air flow path. The needle would function toregulate air flow rate to a low level to, again, afford adequate time towarn the vehicle operator.

Another alternative means for regulating the flow of air through thepassageway 74 would be to incorporate a porous insert body 73 within thepassageway 74 as shown in FIG. 3. The porous insert body 73 would act asa filter and slow the flow of air through the passageway 74 to a ratelow enough to provide time to warn the vehicle operator. The insert bodyor filter 73 may be formed of any suitable porous material that issufficiently durable to withstand the forces encountered. For example,without limitation intended, the insert body 73 may be composed ofsintered metal such as brass. Granular metal may be encapsulated withinthe passageway 74 of the bolt 44. Application of heat and pressure willcause the metal particles to fuse together and form a matrixconstruction. The metal particles will further fuse to the bolt internalsidewalls defining passageway 74, stabilizing the insert and fixing itat an intended location within passageway 74. The degree of filtering orrestriction of air flow through the bolt passageway 74 may be controlledby the size, quantity, and composition of the metal particles used.Higher particle density and lower particle size will provide greater airflow restriction. Forming the filter 73 in place within passageway 74allows for greater uniformity, convenience, and manufacturingefficiency.

In tests, a change of air pressure from 40 psi to 5 psi was made by theremoval of a valve core in a standard inflation valve. The openingresulting therefrom was a bore of 0.15 inches. The opening did not havea sinter metal filter as explained herein. Air pressure loss occurred in½ minute. Two other tests were conducted using bore sizes of 0.1 inchand 0.08 inch, both with a sinter metal filter. The pressure loss from40 psi to 5 psi occurred in 18.5 and 35 minutes, respectively, for the0.1 inch and 0.08 inch bore sizes with sintered metal filter.

While the embodiment of FIGS. 2 and 3 show the regulation of air flowthrough the passageway 74 of bolt connector 44, the invention is notintended to be so limited. Restricting the air flow rate through otherorifices of the rim by the use of a sinter metal body may also beemployed. For example, without an intent to limit the invention, a TPMMsystem may employ multiple through holes through a rim at variouslocations. An aperture, for example, may couple with a pipe that willcommunicate air pressure levels within a tire cavity a distance back toa module 18. If the pipe is damaged and breaks off the assembly duringuse, the same undesirable rapid leakage through the aperture connectingto an end of the pipe could occur. In order to regulate the otherwiseuncontrolled and rapid flow of air through the aperture, the aperturemay be sized small enough to only allow a slow leak down rate.Alternatively, the aperture may be fitted with a needle orifice to slowthe rate of air flow. Still further, the aperture may be fitted with asintered metal insert body that slows the flow of air out of theaperture. The advantage attendant a slowing of the leak down ratethrough the aperture would be the same as described above in referenceto FIGS. 2 and 3; that is to allow sufficient time to warn an operatorof the vehicle before deflation of the tire occurs.

FIGS. 14, 15, and 16 illustrate the gasket 40 in detail. The gasket 40includes sidewalls 84 and having a wall 86. A larger dimensioned chamber76 of circular cross-sectional configuration extends into the gasketwall 86 to an annular flange 78. A flat surface 80 defines a side of thechamber 76 within the gasket. An opening 82 of reduced diameter extendsfrom the annular flange 78 to an opposite side of the gasket. The gasketis formed of a high temperature material such as a fluoro-elastomericmaterial. The washer 42 may likewise be formed of a high temperaturematerial such as a composite metal and elastomeric material.

The transponder board 41 may include temperature and pressure measuringdevices common to the industry. In addition, the board 41 may include IDdata storage and calibration constraints. Operation of the board 41 isto monitor and measure temperature and/or pressure within the tire 14and communicate a signal representing measured values to an externalreader (not shown). Devices suitable for use for such a purpose arecommon and commercially available.

The tire pressure monitoring module 18 is mounted to the rim 12 as willbe apparent from FIGS. 1, 2, and 3. The circuit board 41 is sealedwithin the pressure chamber of the housing 34 by the end cap 36. Thehole 28 is drilled through the rim surface 20 and the bolt 44 extendstherethrough. The washer 42 receives the bolt shaft therethrough andabuts against surface 24 of the rim to prevent air from leaking aroundthe bolt. The housing collar portion 52 receives the annular body 38therein with the annular flange 50 of the housing 34 entering into theannular groove 68 of the insert body. The gasket 40 is positioned overthe housing 34 and receives the collar portion 52 of the housing 34 intothe gasket opening 76. The flat surface 57 of the collar 52 registersopposite the flat surface 80 of the gasket 40 to prevent relativerotation from occurring between the gasket and the housing. The washer42 is inserted into and seats within the gasket opening 82.

The threaded shaft of bolt 44 extends through the washer 42 and thegasket 40 and threads into the insert body threaded bore 70. The tirepressure module 18 is thus firmly affixed to the rim surface 24 andagainst the rim surface 26. In the attached and mounted position, thebore 74 through the bolt 44 is in direct communication with the internalpressure chamber 46 of the housing 34 and the electronics on circuitboard 41 for measuring temperature/pressure. The inflation pressure inthe tire cavity 30 of the tire body 14 is transferred through the bore74 of the bolt 44 to the pressure chamber in the module. The enclosedelectronics within the chamber 46 sense the pressure and transmit anappropriate signal to an external reader.

As seen from FIG. 3, the subject tire pressure monitoring module 18mounts directly to outer surface 24 of rim 12. The module is thusaccessible for replacement or repair should the need arise. Moreover,the bolt head 72 is in direct contact with the tire cavity 30. Thesensor module is mounted on the opposite side of the rim as the tiresand does not contact either tire 14, 16. The pressure monitoring module18 is accordingly in a non-contacting relationship with the tire(s)mounted to the rim 12. Accuracy of the module 18 in measuring airpressure within the tire(s) is accordingly not dependent on maintaininga secure mechanical coupling between the tire and the pressure sensor asis the case with state of the art systems such as valve stem mountedpressure monitoring systems. In racing applications, a plurality ofgrooves 88 are formed within the inner tire 16 and function to allow theair within the cavity 30 of tire 14 to have direct access to the bolthead 72.

From the foregoing, it will be readily apparent that the subject systemthat mounts the pressure monitoring module 18 directly to the rim 12achieves significant advantages. Inflation pressure may be measuredwithout touching the tire(s) and a positive indication of specific tirepressure in the outer tire may be accurately read. The data transmissionprotocol within each module 18 may be designed to prevent one racingteam from reading another team's tire/rim/module systems. Since thevalve stem of the tires is not engaged by the subject invention module18, a mechanical pressure gauge may be used on the valve stem if desiredto validate the measurement of the module 18. Such a redundancy andcross-verification can insure that a correct determination of the tirepressure is made. The module 18 mounts on an outer surface of the rim 12and is thus protected and can survive multiple races in contrast withtire mounted devices that must endure the forces imposed on the devicesby the tire. The module 18 may be incorporated as a standard componentof a tire/wheel assembly and the operation of the module may be verifiedbefore the tire/wheel assembly is released from production. Theelectronics within the module 18 may further work with or withoutelectro-magnetic transmission shields. While only one sensor module 18is shown attached to the rim, multiple modules 18 may be deployed ifdesired, monitoring the same or differing cavities within the tirecomponents.

Additionally, the system incorporates means 44, 73, 74 for controllablyregulating (reducing) the flow of air through the passageway 74 shouldthe module 18 become damaged or detach from the rim 12 during use. Thehousing 34 of the tire pressure monitoring module assembly 18 includesan internal pressure chamber 46; electronics 41 including a pressuresensing device within the housing pressure chamber 46; an elongateconnecting member 44 extending through the housing and the rim mountingsurface, the passageway 74 extending axially through the connectingmember 44 in communication with the internal tire cavity 30 and thehousing pressure chamber 46.

Obstruction of air flow through the passageway through the rim 12 may beby controlling the diameter of the passageway 74 or incorporating ahypodermic needle orifice (not shown), or by incorporating a porousinsert body 73 into the passageway. The insert body 73 may be composedof sintered metal and may be fused in place to the internal sidewalls ofthe bolt defining passageway 74. The matrix construction of the sinteredmetal insert or filter 73 acts to slow down the flow of air through thepassageway 74. Enough time is thereby available to provide the operatorof the vehicle with a warning. The rate of air flow through the filter73 may be varied by design by varying the mass of the sinter metalmaterial composing the filter 73 or by using materials that form filtersof varying particle spacing within the filter. A tighter spacing ofparticles forming the filter 73 would serve to slow the flow of airtherethrough and a wider spacing of particles would allow a higher flowrate. Similarly, the size of the filter 73 within the passageway willaffect the flow rate; a wider filter slowing the flow of air to delaythe leak down versus a narrower filter geometry. Thus, by designing thefilter 73 and passageway size, a controlled leak down may beincorporated. The time interval between a reduction of air pressure from40 psi to 5 psi may thereby be designed into the tire and wheel rimassembly. The time interval may be so designed so as to correspond to anadequate warning time to the user of the tire and wheel assembly.

Variations in the present invention are possible in light of thedescription of it provided herein. While certain representativeembodiments and details have been shown for the purpose of illustratingthe subject invention, it will be apparent to those skilled in this artthat various changes and modifications can be made therein withoutdeparting from the scope of the subject invention. It is, therefore, tobe understood that changes can be made in the particular embodimentsdescribed which will be within the full intended scope of the inventionas defined by the following appended claims.

1. A tire and wheel rim assembly comprising: a tire supporting rimhaving an inward facing tire mounting surface; at least one tire bodymounted to the rim positioning an internal tire cavity over the tiremounting surface; a rim passageway extending through the rim forcommunicating air pressure within the tire cavity to a monitoring devicesecured to an outward side of the rim opposite the tire cavity; the rimpassageway having internal air flow regulating means for operativelycontrolling the air flow rate through the rim passageway from within therim passageway to a controlled non-zero leak-down rate.
 2. A tire andwheel rim assembly according to claim 1, wherein further comprising: themonitoring device comprising at least one tire pressure monitoringmodule assembly mounted to the outward side of the rim and comprising: ahousing having an internal pressure chamber; a pressure sensing devicewithin the housing pressure chamber; an elongate connecting memberextending through the housing and the rim passageway and operativelyconnecting the module assembly to the rim, the connecting member havingan axial passageway extending axially through the connecting member incommunication with the internal tire cavity and the housing pressurechamber.
 3. An assembly according to claim 2, wherein the connectingmember is a bolt extending through the rim and the axial passagewayextending through the bolt.
 4. An assembly according to claim 3, whereinthe air flow regulating means comprises the axial passageway of theconnecting member operatively sized to a controlled reduced diameter. 5.An assembly according to claim 3, wherein the air flow regulating meanscomprises a porous insert body within the axial passageway of theconnecting member.
 6. An assembly according to claim 5, wherein theporous insert body is at least partially composed of sinter metal.
 7. Anassembly according to claim 5, wherein the porous insert body is atleast partially fused to internal bolt sidewalls defining the axialpassageway.
 8. An assembly according to claim 1, wherein the air flowregulating means comprises a connecting member extending through the rimpassageway, the connecting member having an axial passageway diametersized to operatively delay leak down between an upper tire inflationpressure and a lower non-zero tire inflation pressure for a targetedtime interval.
 9. An assembly according to claim 1, wherein the air flowregulating means comprises a porous insert body within an axialpassageway of a connecting bolt extending through the rim passageway.10. An assembly according to claim 9, wherein the porous insert body isat least partially composed of sintered metal.
 11. An assembly accordingto claim 9, wherein the porous insert body is at least partially fusedto internal bolt sidewalls defining the axial passageway.
 12. Anassembly according to claim 11, wherein the porous insert bodyoperatively regulates an air flow through the bolt axial passageway tocontrol leak down from the tire between an upper pressure and a lowernon-zero air pressure for a targeted time interval.
 13. An assemblyaccording to claim 12, wherein the air flow through the porous insertbody is regulated by the mass of porous metal comprising the insertbody.
 14. An assembly according to claim 13, wherein targeted timeinterval comprises a leak down time interval within which to operativelyprovide a warning to a user of the tire and wheel rim assembly.
 15. Anassembly according to claim 1, wherein the air flow through the rimpassageway is regulated within the passageway to control a rate of leakdown from the tire through the rim passageway between an upper tire airpressure and a lower non-zero pressure for a targeted time interval. 16.An assembly according to claim 15, wherein the targeted time intervalcomprises a leak down time interval within which to provide a warning toa user of the tire and wheel rim assembly.
 17. A tire and wheel rimassembly comprising: a tire supporting rim having an inward facing tiremounting surface; at least one tire body mounted to the rim positioningan internal tire cavity over the tire mounting surface; an air pressuremeasuring device secured to an outward side of the rim opposite the tirecavity; an air flow rate regulating passageway extending through the rimfor substantially continuously communicating air pressure between thetire cavity and an internal chamber of the air pressure measuringdevice; and the regulating passageway operatively controls from withinthe passageway a leak down rate of air flow through the passagewaybetween the tire cavity and the outward side of the rim between an uppertire air pressure and a lower non-zero tire air pressure for a targetedtime interval.
 18. The tire and wheel rim assembly of claim 17, whereinthe targeted time interval comprises a leak down time intervalsufficient to provide a warning to a user of the tire and wheel rimassembly.
 19. The tire and wheel assembly of claim 18, wherein the airflow rate regulating passageway comprises an axial bore extendingthrough an elongate connecting member, the connecting member operativelyattaching the air pressure measuring device to the outward side of therim.
 20. The tire and wheel assembly of claim 19, wherein the air flowrate regulating passageway further comprises a porous insert bodysituated within the axial bore of the connecting member.